CN1123033A

CN1123033A - Additives for polymer compositions

Info

Publication number: CN1123033A
Application number: CN95190075A
Authority: CN
Inventors: A·L·布安; D·劳林
Original assignee: Baxter International Inc
Current assignee: Baxter International Inc
Priority date: 1994-02-09
Filing date: 1995-02-03
Publication date: 1996-05-22
Also published as: ZA951041B; WO1995021885A1; US5643501A; CA2158548A1; JPH08509022A; IL112553A0; EP0694052A1; KR960701934A

Abstract

An additive system for a polyvinyl chloride formulation for improved processability while maintaining thermal stability of the formulation, and having a low-water-blush haze and low extractability in an aqueous media, the additive system including a primary stabilizer which is a Lewis acid metal compound selected from the group consisting of organo-tin compounds and organo-zinc compounds, a secondary stabilizer selected from the group consisting of epoxide compounds having less than approximately 5.2 oxirane groups per molecule; and, an external lubricant for lubrication of the PVC formulation, wherein a critical ratio of the primary stabilizer to the secondary stabilizer maximizes thermolytic color stability while limiting generation of excessive build-up, plate-out, dark particles during the processing of the polyvinyl chloride formulation. And wherein the invention provides concentration levels of the stabilizers and an oxirane per molecule content of the secondary stabilizer which minimizes the extractables in aqueous media.

Description

Additives for polymer compositions

RELATED APPLICATIONS

This application is a continuation-in-part application entitled "additives for vinyl chloride polymer compositions" filed on 27.5.1992, U.S. application No.07/889, 550.

The present invention relates to vinyl chloride polymer compositions for medical applications. More specifically, the present invention relates to the stabilization of a flexible, plastic vinyl chloride polymer composition used in the manufacture of sterilizable medical devices.

Most polymer compositions are useful for making extruded and molded articles (e.g., flexible packaging containers, hose applications), as well as injection molded articles. For example, in the medical industry, flexible packaging containers and tubing sets are used, inter alia, for packaging and delivering parenteral fluids (e.g., intravenous fluids, dialysis fluids), pharmaceuticals and medicaments, nutraceuticals, respiratory therapies, blood, plasma, and other blood-related products. When such desirable products are used in the medical industry, they will frequently contain or contact fluids or solids that will enter the patient. Therefore, these appliances must be substantially transparent; is flexible; substantially free of solubles; does not absorb the contained fluid or solid; substantially free of particulate matter; and under sterile conditions, the article packaged therein can be stored until the article is used or removed. The plastics from which these containers, tubes and other articles are constructed mustalso meet these requirements.

It is important that the plastic from which the containers, tubes and other articles are constructed be strong enough to provide sufficient strength to the products constructed from the plastic. Furthermore, for economic reasons, it is desirable that any such plastic be easily processed into containers, tubes or other articles commonly used in the industry, or be easily reworked and used in the manufacture of devices. Factors such as productivity, material stability, particulate matter production, scrap rate and the potential need for regrinding must be considered strictly in determining the processability of any plastic used to construct such products.

As discussed above, because plastics are processed into flexible containers and other medical devices for containing or contacting medical articles that are to be introduced into a patient, the plastics must be free of chemicals that may be extracted by the medical articles or that may be introduced into the patient with the medical articles. Most notable are the various additives in the polymer composition that are used to impart flexibility, general processability and stability to the plastic. The toxicity of such additives has been a concern and a monitored issue.

Medical devices such as iv bags, dialysis containers, blood bags, drug delivery devices and tubing are typically sterilized at high temperatures or by chemical sterilants such as ethylene oxide gas. However, in the case of high-temperature sterilization, there is a problem that synthetic resins used for such medical containers, tubes and other articles are required to be resistant to thermal degradation. In the case of sterilization using ethylene oxide gas, there has been a problem that it takes a lot of time to completely remove ethylene oxide gas from sterilized medical containers, tubes and other articles after the sterilization. As an alternativemethod, radiation sterilization has been proposed. Since this process can be carried out at low temperatures, the materials of medical containers, tubes and other articles are no longer required to be resistant to heat and thermal degradation. Unless plastics are specialized compositions, radiation can cause adverse effects of quality degradation, such as discoloration of irradiated medical containers, tubes, and other articles, clouding when exposed to water after irradiation, and increased extractables.

Vinyl chloride polymer ("PVC") has many excellent properties that make it one of the major industrial plastics in the world. In the medical industry, PVC is widely used for many applications including infusion containers for intravenous fluids and pharmaceuticals, dialysis containers, blood bags, solution administration sets, tubing, and other molded articles. The processing and utilization of PVC for these medical applications relies on various plasticizers, stabilizers, and other additives, but also introduces some other potentially adverse properties. For example, flexible containers and hoses are generally required to have low extractables, low absorbency, low tendency to cause hazy water spotting, low color, good clarity, and the liquid carried by the container or tube should not be contaminated by particulate matter. In the production process, plasticizers, stabilizers and other additives are generally used in order to improve the processability of PVC, to shorten the production time, to reduce the wear and tear on equipment, to eliminate particles, to reduce the rejection rate and to increase the utilization of regrind. Ultimately, PVC containers must remain stable during manufacture, processing, and use.

The accepted weakness of PVC is thermal instability in processing and use, thereby leading to HCl elimination and conjugated unsaturated states, and increased discoloration due to increased conjugation length. Thermaldegradation can be delayed by the addition of certain selected combinations of stabilizers, typically calcium soaps, zinc soaps, organotin compounds including esters of dialkyltin such as alkyl carboxylates (e.g., laurates and stearates), di-n-octyltin maleate polymers and di-n-octyltin S, S' -mercaptoacetates, epoxidized aliphatic esters and organic phosphites.

The use of low levels of stabilizers to meet the low levels of extractables required for such medical containers, tubing and other articles can result in degradation of the PVC and thus can be difficult to stabilize and process. However, this low level of stabilizer has the opposite positive effect by reducing the aqueous draw-off of the PVC film. Higher amounts of processing aids and stabilizers may be used when higher extractable levels are permitted or the stability of the PVC is more critical, but processing difficulties are encountered in known extrusion molding processes from "fouling" by "clinkers" or crosslinked ("cured") epoxies caused by excess lubricants, as well as "fouling" by other processing aids formed on the die and chilled rolls.

Early attempts to provide stabilizer systems for PVC failed most due to the incorporation of ingredients that resulted in high extractables, poor processability due to settling and fouling on equipment, severe water spotting and high color. For example, U.S. Pat. No.3,558,539 discloses a stabilizer system for PVC comprising 5 components which are long chain aliphatic monocarboxylic acid salts of calcium and magnesium, tri-substituted organic monophosphites, and tri-substituted organic polyphosphites. The addition of these ingredients to a PVC stabilizer system, when the stabilized PVC film is autoclaved at 121 ℃, results in high water-spotting turbidity and high levels of low molecular weight water-soluble compounds result in high concentrations of extractables.

As another example, U.S. patent No.4,571,118 discloses a stabilizer system that results in high water spotting and high extraction. The stabilizer system for PVC disclosed in the US4,571,118 patent comprises a calcium soap in addition to compounds having the general formulae OH-X-O-R and R-O-X-O-R, wherein X is a linear, branched or cyclic group having 2 to 20 oxygen atoms. These compounds also lead to high extraction and high water-spotting when autoclaved on stabilized PVC at 121 ℃.

Summary of the invention

The present invention provides a variety of additive systems for PVC compositions to further improve processability and functional properties of medical devices made from PVC. These additive systems unexpectedly outperform previously known systems in terms of both PVC melt production and thermal stability (e.g., increased thermal stability, faster melt flow during extrusion without discoloration or black particle formation, reduced settling or fouling on processing equipment, reduced scrap and equipment down time, improved utilization of regrind), and desirable product properties (e.g., low color, haze, water spotting, extractables, and particle formation).

The additive system of the present invention includes a primary stabilizer, a secondary stabilizer, and an external lubricant. The additive system of the present invention preferably comprises a combination of a zinc salt primary stabilizer and an epoxide secondary stabilizer in critical amounts and a polyethylene external lubricant. Other processing aids and performance additives, such as antioxidants, colorants, antimicrobials, and internal lubricants, may also optionally be included, so long as they are not detrimental to the intended results discussed herein.

These additive systems are useful in rigid PVC, semi-rigid PVC, or flexible PVC applications. For example, the additive system of the present invention provides stability and processability to low plasticized or unplasticized PVC compositions that can be used in injection molding to produce rigid or semi-rigid products such as filter housings, medical sinks and containers, and the like. Likewise, the additive system of the present invention also provides stability and processability to plasticized PVC compositions typically used to produce flexible medical containers and hoses that come into contact with fluids (e.g., intravenous fluids, peritoneal dialysis solutions, blood and blood products, etc.). Known plasticizers generally include dialkyl phthalates, trialkyl trimellitates, alkyl or aryl benzoates, citrates, and polymeric plasticizers such as polyurethanes, ethylene-vinyl acetate-carbon monoxide terpolymers, and polyesters.

The PVC compositions of the present invention function even within a wide temperature range beyond the glass transition temperature of the composition. The PVC composition can be retort sterilized at 121 ℃ without causing problems with water extraction, water spotting, color, haze and particle formation required for medical applications.

The following detailed description of the preferred embodiments clearly describes additional features and advantages of the present invention. Brief description of the tables

Table 1 shows PVC test data and the stabilizer system of the present invention. Detailed description of the preferred embodiments of the invention

The present invention provides additive systems for PVC compositions to further improve the processability of the materials and the functional properties of medical containers, hose fittings and molded articles made from such materials. Preferred additive systems of the present invention comprise a primary stabilizer (e.g., a Lewis acid metal compound) and a secondary stabilizer in a strict amount ratio. The additive system also includes an external lubricant.

The primary stabilizer is selected from Lewis acid metal compounds, such as organotin compounds and organozinc compounds, the organotin compounds including esters of dialkyltin, such as alkylcarboxylates(e.g., laurates and stearates), di-n-octyltin maleate polymers and di-n-octyltin diisooctyl S, S' -thioglycolate; the organozinc compound includes alkyl carboxylates such as zinc salts of fatty acids (laurate, palmitate, stearate, erucate, behenate)Acid salts, rosin acid salts, etc.) and zinc salts based on ionomers derived from monomers such as ethylene, alkyl acrylates or styrene in combination with monomers such as acrylic acid, fumaric acid, or maleic acid. The amount of the primary stabilizer used in the PVC composition is 0.02 to 0.5 part per 100 parts of PVC resin (hereinafter referred to as "phr"). The primary stabilizer is preferably zinc stearate, preferably in an amount of about 0.05 to 0.3phr, and most preferably in an amount of 0.1 phr. One advantage of zinc stearate is that it provides high optical clarity, both before and after sterilization with steam, ethylene oxide or radiation.

The secondary stabilizer of the present invention is selected from the group consisting of epoxides which are sufficiently compatible with the PVC and other compounding ingredients that it dissolves in the PVC and maintains this dissolved state during processing and use to provide thermal stability to the PVC composition. Most epoxies are also good PVC thickeners, some of which can be used in the composition as the sole or primary plasticizer. These epoxides may be used alone or in combination as desired. Suitable epoxides include, but are not limited to, glycerol trioleate, epoxidized linseed or soybean oil or partially hydrogenated unsaturated vegetable oils with low ethylene oxide content, propylene glycol diepoxide oleate, and copolymers of glycidyl acrylate (glycidyl). The secondary stabilizer contains less than about 5.2 ethylene oxides per molecule and at least one ethylene oxide per molecule. The auxiliary stabilizer is used in the PVC composition in an amount of 5 to 100phr according to the requirements of the use of the composition. For example, if the additive system is to be incorporated into plasticized PVC for soft goods (i.e., soft medical containers), the preferred range of secondary stabilizers is from about 10 to about 20 phr. Similarly, if the additive system is to be added to unplasticized PVC for soft goods, the preferred range may be approximately 40 to 80 phr. In the present invention, the preferred co-stabilizer is propylene glycol diepoxide oleate, which usually contains 2.5 ethylene oxides per molecule. It has furthermore been found that the purity of the epoxide is a decisive factor in the PVC compositions obtained with low extractability in aqueous solutions, biological fluids and cell tissue. Therefore, it is desirable to have epoxides with low concentrations of low molecular weight water soluble by-products in the epoxidation process.

This group of secondary stabilizers does not include metal ions selected from group IA or IIA of the periodic Table of the elements, and their use is known to result in the formation of cloudy water spots when the composition plastic encounters water, whether liquid or vapor.

For practical production such as the PVC composition of the invention, melt processing is necessary. The external lubricant provides lubricity and is isolated from the metal of the processing equipment; for example, the screw, die and film chill roll of a film extruder; or for example the screw, sprue and runner of an injection moulding machine. The practical benefits of such lubrication for film extrusion are: (i) faster melt flow, (ii) lessthermal and shear stress degradation that can lead to discoloration, black spots, lower molecular weight placement and more water extraction byproducts, (iii) prevention of mold scratching and (iv) prevention of loose particles on the film caused by fouling of the degraded and crosslinked material on the die lips, while reducing blocking between the film and chilled rolls, and between the finished film and film. However, the concentration of lubricant must be sensitively balanced with the benefits obtained, no excess lubricant should be present, otherwise poor melt transport (e.g. overall process) is caused, the lubricant precipitates on the die and extrusion equipment forming scale (scratches on the film, loose particles and degraded material) and precipitates on the chilled roll forming scale (loose particles on the film).

External lubricants, which are common in PVC compositions, are concentrated on the surface of the flowing melt during processing due to their incompatibility with other ingredients in the molten polymer composition. The most common epoxide stabilizers and Lewis acid metal compounds (and their by-products) in PVC compositions are also concentrated rheologically on the surface of the flowing melt due to their lower viscosity than PVC. The mixture on the surface of the flowing melt is therefore enriched with epoxide, Lewis acid metal compound by-products, lubricants and protonic acids (HCl and carboxylic acids are formed by the HCl elimination of PVC and are subsequently neutralized by the carboxylic acid soaps of the stabilizer system). The lewis acid metal compound (and by-products thereof) and the protonic acid act as an initiator (a crosslinking initiator) causing the epoxide to polymerize, crosslink, and thus adhere to the metal surfaces of the processing equipment, while binding with the external lubricant and carrying the lubricant away from the surface of the flowing melt.

The toughness and degreeof build-up of such plate-out depends not only on the viscosity, concentration, amount of these ingredients and the reactivity of the ethylene oxide, but also on the polymerization molecular weight and crosslink density, which in turn depend on the concentration ratio of the epoxide to the crosslinking initiator, as well as the number of ethylene oxide groups and their proximity in epoxide (i.e., the ethylene oxide equivalent weight of the epoxide). Thus, there is a critical ratio between epoxide and initiator that minimizes settling while providing sufficient material stability and low pump-out for use with aqueous fluids. Preferably, the ratio of the Lewis acid metal compound to the ethylene oxide is 0.0015-0.006, preferably 0.002-0.0055, and most preferably 0.0035.

External lubricants useful in the present invention include, for example, polyethylene, oxidized polyethylene, polyvinyl ionomer, polyfluorocarbon (e.g., TFE, FEP, VF2, perfluoroethyl ether containing polymer), paraffin, ester wax, amide wax, polyethylene oxide, copolymers of ethylene oxide and propylene oxide, polyamides, polypeptides, polyvinyl alcohol, ethylene-vinyl alcohol copolymers. Copolymers of polyalkylacrylates and polyhydroxyalkylmethacrylates, copolymers of acrylic acid or its salts, copolymers of maleic anhydride with ethylene, propylene or styrene, polymers containing sulfonic acid groups and their salts, and sulfonated polyarylsulfones. The lubricants of the present invention must be stable during processing and use and not allow contamination of medical or biological agents in contact with the PVC composition. Each of these lubricants can be used alone or in combination with several, and their concentrations and epoxide to initiator ratios are maintained at the optimum values provided, as described above. Typically, the lubricant is added in an amount of 0.01 to 1.0phr PVC. A preferred lubricant is polyethylene, which is added in an amount of between 0.015phr and 0.05phr, preferably between 0.025 and 0.050phr, and most preferably 0.025 phr.

The properties of the PVC compositions of the invention, as we have already known, depend on a suitable balance between the amounts and the nature of the primary and secondary stabilizers and of the external lubricant. A proper balance of stabilizers and lubricants is especially necessary in order to obtain low color, low extractables, and little or no precipitation on the melt processing equipment surfaces. During melt processing (i.e., compounding or production), acid-catalyzed polymerization and crosslinking of the epoxy compound at the surface of the molten PVC composition can result in precipitation which causes the external lubricant to adhere strongly to the metal surface in contact with the melt through the epoxy. This adhesion strength depends on the molecular weight and crosslink density of the polymerized epoxide, which in turn is greatest at some moderate equivalent ratio of epoxide to acid initiator, which can be, for example, a strong lewis acid byproduct of the primary stabilizer (e.g., tin chloride or zinc chloride).

Since deposits often fall off the processing equipment and adhere loosely to the plastic surface, preventing or minimizing such deposits necessarily reduces the incidence of loose particles present in the feed fluid onto the plastic surface. In addition, the avoidance of deposits also prevents particles (usually black dots) released from the highly degraded deposits from contaminating the PVC article on the hot metal surfaces of the melt processing equipment. Using this theory we are even able to prevent deposits on troublesome surfaces which are susceptible to reaction with epoxides and which have high surface energies (typically above 40 dynes/cm), such as metal surfaces commonly used in melt processing plasticized PVC compositions. The PVC compositions of the present invention are believed to support this explanation by observing the extrusion and injection molding of the deposited material compositions and analyzing them.

In a preferred embodiment of the invention, as lubricant, a high density linear polyethylene of suitably high melt viscosity is used, having a melt index in the range of 0.5 to 3.0, and constituting about 0.015% by weight in the PVC composition; as an auxiliary stabilizer, propylene glycol diepoxide oleate is used in an amount of about 9.1% by weight; as the primary stabilizer, about 0.063 wt% zinc stearate (buffered with stearic acid) was used. The PVC composition with the preferred additive system, plasticized with about 28 weight percent diethylhexyl phthalate, is extruded into a film on a 4 to 1/2 inch extruder at high throughput rates (e.g., 8001000 pounds per hour) without the occurrence of deposits, discoloration, black spots or loose particles. Furthermore, the PVC composition with the preferred additive system is injection molded without discoloration, black spots or sticking to the mold. Articles made from PVC with this preferred additive system can be sterilized by irradiation, steam or ethylene oxide without excessive discoloration (15 mil thick films with yellowness index below 2) and without draw-off or toxicity. Moreover, flexible containers for pharmaceutical or biological fluids made from PVC with this preferred additive system retain good clarity after steam sterilization (e.g., 15 mil thick films with a water induced appearance haze of less than 6% and a permanent haze of less than 2% as measured immediately after autoclaving).

Table 1 lists several processing and performance tests of film samples compared between the preferred embodiment of the present invention and other commercial PVC compositions. Each film sample tested was plasticized with an equal amount of diethylhexyl phthalate.

Stirring the following components under strong forceMixed in a blender and extruded into 15 mil thick films using a single screw extruder. A promising agent for use in the following compositions is diethylhexyl phthalate ("DEHP"). The secondary stabilizer can be either an epoxidized linseed oil ("ELO") or a propylene glycol diepoxide oleate ("PGBEO"). The primary stabilizer is selected from zinc stearate (' ZnSt)₂") or 50/50 mixtures of calcium stearate and zinc stearate (" ZnSt₂＋CaSt₂"). The lubricant is selected from the high density polyethylene ("HDPE") or ethylene bis-acetyl sulfonamide ("EBS") described above.

The examples contain: 100 parts of PVC, 44 parts of DEHP, 14.5 parts of PGBEO, 0.025 part of HDPE and 0.1 part of ZnSt₂。

Comparative example 1 contains: 100 parts of PVC, 44 parts of DEHP, 14.5 parts of ELO, 0.4 part of EBS and 0.2 part of ZnSt₂＋CaSt₂。

Comparative example 2 contains: 100 parts of PVC, 44 parts of DEHP, 14.5 parts of ELO, 0.025 partsHDPE and 0.29 part of ZnSt₂。

Comparative example 3 contains: 100 parts of PVC, 44 parts of DEHP, 14.5 parts of PGBEO, 0.2 part of EBS and 0.1 part of ZnSt₂＋CaSt₂。

Comparative example 4 contains: 100 parts of PVC, 44 parts of DEHP, 14.5 parts of PGBEO, 0.025 part of HDPE and 0.2 part of ZnSt₂。

The sequence of color characteristic changes (colorless and transparent → yellow → orange → red → brown) exhibited by PVC when heated is typical of a system that expands into longer and longer conjugated polyene segments. PVC is quite sensitive to even mild heating and the formation of visible colour is often the first obvious indicator of degradation. These changes occur well before any more severe phenomena of degradation become apparent. If heating is continued, a physical change will occur.

The color stability tests of static heat (incubator) and dynamic heat (Brabender tester) provide an indication of the early color formation to the HCl elimination. These stability tests are close to the degradation observed during extrusion of PVC films by known processes.

The thermal stability can be determined by measuring the yellowness index of a sample film having the additive system described above. Strips of the sample film were placed in an air circulating aging oven at 370 ° F (188 ℃), and the strips were periodically removed for testing. The yellowness index is determined by known methods using a colorimeter available from Hunter corporation. The films with the preferred additive systems ("examples") exhibited the best color stability throughout the time of the test as evaluated by the sample films. Furthermore, the film samples containing the preferred additive system showed the same static thermal stability as the film samples made with 30% regrind.

In a Brabender Fusion Head (Brabender Fusion Head), melting and shearing of PVC material in air initially causes HCl elimination, resulting in a gradual degradation of the color. The crosslinking is immediately followed by this HCl-off action, which is evidenced by the increase in viscosity, thickening and dramatic darkening of the color of the PVC material. The brabender test differs from the thermal aging test in that shear forces are applied to the material during the time the material is heated to a specified temperature. The results of the Brabender test therefore depend not only on the thermal stability but also on the melt lubrication effect formed by the compounding ingredients. This is very close to the conditions to which PVC material is subjected in melt production processes such as extrusion or injection moulding. Also, the reuse of crushed burrs or regrind material means that the PVC material is subjected to more thermal and melt shear stress. Thus, this test can be used to simulate the situation where regrind material is added to an extruder or die press with fresh material repeatedly over and over.

The yellowness index was determined on samples of PVC film with the above additive system. The original film samples were made using the known extrusion method described above (number of passes ═ 0). The raw sample was then placed in a brabender apparatus and treated in air at 370 ° F (188 ℃) for 20 minutes at 60rpm (number of treatments 1). The re-pulverized material was reused 4 times, and 70% of the samples in each time were fresh materials and 30% of the samples in the previous time were re-pulverized (treatment times 2, 3, 4, 5). For example, in sample 2, 70% was virgin material and 30% was reground film material from sample 1. Film samples (examples) with the preferred additive system showed the best color stability under processing conditions similar to those typical of known extrusion processing (heat, shear and doping regrind).

Furthermore, it is known that the primary stabilizer is a Lewis acid metal compound, preferably zinc stearate; the secondary stabilizer is an epoxide, preferably propylene glycol diepoxide oleate, and the critical concentrations of primary and secondary stabilizers produce surprising and unexpected effects on thermal stability (expressed as yellowness index). We also know that the critical ratio of primary to secondary stabilizer allows to obtain unexpected processability (low deposition, low black spot) of PVC materials.

Lewis acid metal compounds, e.g. zinc stearate ("ZnSt₂") act in a well-known manner to replace the chlorinated hydrocarbon active on PVC, as per equation (1), and neutralize the hydrochloric acid as per equation (2).

Too high a concentration of zinc stearate (e.g. comparative example 4) results in an increase in zinc chloride which will further catalyze the degradation and HCl removal of PVC. We have found that excess zinc chloride also acts as an epoxide crosslinking initiator, causing more deposition during extrusion and more black spots during extrusion or injection molding. It follows that too much zinc chloride causes a loss of ethylene oxide, resulting in a further loss of stability. Conversely, if the concentration of zinc stearate is too low (e.g., comparative example 3), the PVC will undergo HCl elimination to form HCl, which accelerates this degradation process and initiates the crosslinking depletion of the ethylene oxide.

The stabilization by the addition of a critical amount of epoxide is due to the fact that it reacts with the active oxygen-containing hydrocarbon on the PVC preventing the formation of acid (equation 3) while removing the zinc chloride (equation 4).

ZnClX + HO-R' -R-Cl wherein X is-OH or stearate.

However, too high a concentration of epoxide does not provide better color stability, but results in more cross-linked epoxide initiated by the acid generated during heating. In addition, low concentrations of epoxide are rapidly consumed and thus are not sufficient to provide stable protection.

By utilizing the preferred additive system, higher processing efficiency and material savings are realized. As shown in Table 1, we have surprisingly found that there is no more material deposition or fouling on the processing equipment when using the additive system of the present invention. Thus, a greater amount of lubricant can be used to improve melt processing without deposits. The extrusion die has no precipitation adhesion layer andno scale on the chilled roller, thereby saving the downtime of the extrusion equipment. Furthermore, during the processing, black spots due to fouling no longer occur in the melt processing equipment. Compared with the PVC material available at present, the waste rate is reduced by about 20-30% when the additive system is used.

Improved product properties are also obtained when the PVC material with the additive system of the invention is used to make products. For example, medical containers, bottles, hoses, etc. made from such PVC materials still have low extractables and improved clarity after steam sterilization. Extractables in medical containers constructed from extruded films of PVC compositions containing the various additive systems described above were tested according to the method of the japanese pharmacopoeia No. XII monograph ("JPXII"). The film samples were cut into strips and autoclaved in 200ml of distilled or deionized water at 121 ℃ for 1 hour. The aqueous extract was analyzed for zinc, ammonia, and oxidizable substances content, pH change, and ultraviolet absorbing substances (wavelengths 241 and 220 nm).

Table 1 shows the values for JPXII process extractables for samples of film material with or without regrind, which further confirms that the film material containing the PVC additive system of the present invention is within the allowable specifications of the JPXII standard.

Deposition/fouling was determined by extruding the PVC material through a die into a film and dropping the film onto a chilled roll. The chilled rolls were then checked for deposit buildup. If deposition/fouling is observed, then "with" is filled in Table 1. The particles are determined by observing the extruded film for visible particles in or on the surface. If particles are observed, "with" is filled in Table 1.

It will be understood that various changes andmodifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. For example, it is envisioned that the inventive additive system is also very useful for chlorinated polyolefins such as chlorinated polyethylene, chlorinated polypropylene, and PVC. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended to include within the scope of the appended claims all such changes and modifications.

TABLE 1

Test items	Ultraviolet ray 220nm	Ultraviolet ray 241nm	Zinc (ppm)	Oxidizable compound (ml)	ΔpH	Ammonium salt (ppm)	Deposit- Scale deposit	Particulate matter
Test items	Ultraviolet ray 220nm	Ultraviolet ray 241nm	Zinc (ppm)	Oxidizable compound (ml)	ΔpH	Ammonium salt (ppm)	Deposit- Scale deposit	Particulate matter	Allowance of	0.08a.u.	0.05a.u.	NMT 0.5	NMT 1.0ML	NMT 1.0	NMT 0.5	No applicable data	No applicable data
Examples 1 set of experiments A Experiment B	0.051 0.057	0.031 0.031	0.27 0.26	0.48 0.38	-0.74 -0.82	＜0.5 ＜0.5	No	No	Allowance of	0.08a.u.	0.05a.u.	NMT 0.5	NMT 1.0ML	NMT 1.0	NMT 0.5	No applicable data	No applicable data
Examples 1 set of experiments A Experiment B	0.051 0.057	0.031 0.031	0.27 0.26	0.48 0.38	-0.74 -0.82	＜0.5 ＜0.5	No	No	2 groups of experiments A Experiment B	0.045 0.055	0.027 0.029	0.24 0.24	0.40 0.40	-0.73 -0.80	＜0.5 ＜0.5	No	No
3 groups of experiments A Experiment B	0.048 0.043	0.027 0.026	0.26 0.26	0.45 0.40	-0.82 -0.82	＜0.5 ＜0.5	No	No	2 groups of experiments A Experiment B	0.045 0.055	0.027 0.029	0.24 0.24	0.40 0.40	-0.73 -0.80	＜0.5 ＜0.5	No	No
3 groups of experiments A Experiment B	0.048 0.043	0.027 0.026	0.26 0.26	0.45 0.40	-0.82 -0.82	＜0.5 ＜0.5	No	No	Example, 30% by weight regrind 1 set of experiments A Experiment B	0.048 0.051	0.029 0.029	0.27 0.26	0.52 0.38	-0.84 -0.84	＜0.5 ＜0.5	No	No
Comparative example 1	0.157	0.067	-	1.01	-0.4	＜0.5	No	Yes		0.048 0.051	0.029 0.029	0.27 0.26	0.52 0.38	-0.84 -0.84	＜0.5 ＜0.5	No	No
Comparative example 1	0.157	0.067	-	1.01	-0.4	＜0.5	No	Yes	Comparative example 2	0.151	0.050	-	3.63	-0.79	＜0.5	Yes	No
Comparative example 3 1 set of experiments A Experiment B	0.046 0.053	0.030 0.034	0.12 0.11	0.32 0.36	-0.65 -0.57	＜0.5 ＜0.5	No	Yes	Comparative example 2	0.151	0.050	-	3.63	-0.79	＜0.5	Yes	No
Comparative example 3 1 set of experiments A Experiment B	0.046 0.053	0.030 0.034	0.12 0.11	0.32 0.36	-0.65 -0.57	＜0.5 ＜0.5	No	Yes	Comparative example 4 1 set of experiments A Experiment B	0.031 0.027	0.027 0.027	0.59 0.61	0.5 0.35	-0.40 -0.2	＜0.5 ＜0.5	Yes	Yes

Claims

1. an additive system for polyvinyl chloride composition, it has kept the thermostability of composition when improving workability, it is characterized in that, this additive system comprises:

A primary stabilizer which is a Lewis acid metal compound selected from the group consisting of organotin compounds and organozinc compounds;

an auxiliary stabilizer selected from the group consisting of epoxy compounds having less than about 5.2 oxirane groups per molecule; and

An effective amount of external lubricant for the lubrication of PVC compositions,

Among them, the ratio of the main stabilizer to the auxiliary stabilizer maximizes the color translation stability of pyrolysis, and at the same time limits the generation of excessive fouling, sedimentation and black spots during the processing of the polyvinyl chloride composition .

2. The additive system as claimed in claim 1, characterized in that the primary stabilizer is zinc stearate, and its consumption is about 0.02-0.5 parts per 100 parts of PVC.

3. The additive system as claimed in claim 1, wherein the auxiliary stabilizer is propylene glycol diepoxy oleate, and its consumption is about 5 to 100 parts per 100 parts of PVC.

4. The additive system as claimed in claim 1, characterized in that the external lubricant is a linear high density polyethylene having a melt index of 0.5 to 3.0.

5. An additive system for a polyvinyl chloride composition, which maintains the thermal stability of the composition while improving processability, characterized in that the additive system comprises:

A primary stabilizer, which is a Lewis acid metal compound selected from the group consisting of organotin compounds and organozinc compounds, and its dosage is about 0.02 to 0.5 parts per 100 parts of PVC;

An auxiliary stabilizer selected from the group consisting of epoxy compounds having less than about 5.2 oxirane groups per molecule in an amount of about 5 to 100 parts per 100 parts of PVC ;as well as

An effective external lubricant for the lubrication of PVC compositions.

6. Additive system as claimed in claim 5, characterized in that the primary stabilizer is derived from esters of dialkyltin, polymers of di-n-octyltin maleate and S, S'-diisooctyl mercaptoacetate An organotin compound selected from the group consisting of di-n-octyltin.

7. The additive system of claim 5, wherein the primary stabilizer is selected from the group consisting of alkyl carboxylates including zinc salts of fatty acids and zinc salts of ionomers Organozinc compounds, said ionomers are formed on the basis of monomers such as ethylene, alkyl acrylate or styrene combined with acrylic acid, fumaric acid or maleic acid.

8. The additive system as claimed in claim 5, characterized in that the primary stabilizer is zinc stearate.

9. The additive system of claim 5, wherein the co-stabilizer has about 2.5 ethylene oxide per molecule.

10. The additive system as claimed in claim 5, characterized in that the co-stabilizer is diepoxypropylene glycol oleate.

11. The additive system as claimed in claim 5, characterized in that the external lubricant is selected from the group consisting of polyethylene, oxidized polyethylene, ionomers of polyethylene, polyfluorocarbons, paraffins, ester waxes , amide waxes, polyethylene oxides, copolymers of ethylene oxide and propylene oxide, polyamides, polypeptides, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyhydroxyalkyl acrylates and polyhydroxyalkyl methacrylates Copolymers, copolymers of acrylic acid or its salts, copolymers of maleic anhydride with ethylene, propylene or styrene, polymers containing sulfonic acid groups and their salts, and sulfonated polyarylsulfones.

12. The additive system as claimed in claim 5, characterized in that the external lubricant is a linear high density polyethylene having a melt index of 0.5 to 3.0.

13. The additive system of claim 5, wherein the primary stabilizer is used in an amount of about 0.05-0.3 parts per 100 parts of PVC.

14. The additive system as claimed in claim 5, characterized in that the auxiliary stabilizer is used in an amount of about 10-20 parts per 100 parts of PVC.

15. The additive system as claimed in claim 5, characterized in that the auxiliary stabilizer is used in an amount of about 40-80 parts per 100 parts of PVC.

16. A medical product made from a polyvinyl chloride composition having an additive system comprising:

about 0.06% by weight of a primary stabilizer which is a Lewis acid metal compound selected from the group consisting of organozinc compounds;

about 9.1% by weight of a secondary stabilizer selected from the group consisting of epoxy compounds having less than about 5.2 oxirane groups per molecule;

About 0.015% by weight external lubricant.

17. The medical product as claimed in claim 16, characterized in that it is produced by extrusion of a polyvinyl chloride composition with an additive system.

18. The medical product as claimed in claim 16, characterized in that it is produced by injection molding a polyvinyl chloride composition with an additive system.

19. The medical product as claimed in claim 16, characterized in that the product is used to contain aqueous solutions, biological fluids and cell tissues.

20. The medical product as claimed in claim 16, characterized in that the product is a tube.

21. An additive system for a polyvinyl chloride composition, which maintains the thermal stability of the composition while improving processability, characterized in that the additive system substantially comprises:

an auxiliary stabilizer selected from the group consisting of epoxy compounds having less than about 5.2 oxirane groups per molecule, and

Among them, the ratio of the main stabilizer to the auxiliary stabilizer maximizes the color stability of pyrolysis, and at the same time limits the generation of excessive fouling, sedimentation and black spots during the processing of the polyvinyl chloride composition.

22. The additive system as claimed in claim 21, characterized in that the primary stabilizer is zinc stearate in an amount of about 0.02-0.5 parts per 100 parts of PVC.

23. The additive system as claimed in claim 21, characterized in that the auxiliary stabilizer is propylene glycol diepoxy oleate in an amount of about 5-100 parts per 100 parts of PVC.

24. The additive system of claim 21, wherein the external lubricant is a linear high density polyethylene having a melt index of 0.5 to 3.0.

25. An additive system for a polyvinyl chloride composition which improves processability while maintaining a thermal stabilizer of the composition, characterized in that the additive system essentially comprises:

An auxiliary stabilizer selected from the group consisting of epoxy compounds having less than about 5.2 oxirane groups per molecule in an amount of about 5 to 100 parts per 100 parts of PVC; as well as

An effective amount of an external lubricant for the lubrication of PVC compositions.

26. The additive system as claimed in claim 25, characterized in that the primary stabilizer is selected from esters of dialkyltin, polymers of di-n-octyltin maleate and S, S'-diisooctyl thioglycolate An organotin compound selected from the group consisting of di-n-octyltin.

27. The additive system of claim 25, wherein the primary stabilizer is selected from the group consisting of alkyl carboxylates including zinc salts of fatty acids and zinc salts of ionomers Organozinc compounds, said ionomers are formed on the basis of monomers such as ethylene, alkyl acrylate or styrene combined with acrylic acid, fumaric acid or maleic acid.

28. The additive system of claim 25, wherein the primary stabilizer is zinc stearate.

29. The additive system of claim 1, 16, 21 or 25, wherein the co-stabilizer has about 2.5 ethylene oxide per molecule.

30. The additive system of claim 25, wherein the co-stabilizer is diepoxypropylene glycol oleate.

31. The additive system as claimed in claim 25, characterized in that the external lubricant is selected from the group consisting of polyethylene, oxidized polyethylene, ionomers of polyethylene, polyfluorocarbons, paraffin waxes, ester waxes , amide waxes, polyethylene oxides, copolymers of ethylene oxide and propylene oxide, polyamides, polypeptides, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyhydroxyalkyl acrylates and polyhydroxyalkyl methacrylates Copolymers, copolymers of acrylic acid or its salts, copolymers of maleic anhydride and ethylene, propylene or styrene, polymers containing sulfonic acid groups and their salts, and sulfonated polyaryl sulfones.

32. The additive system of claim 25, wherein the external lubricant is a linear high density polyethylene having a melt index of 0.5 to 3.0.

33. The additive system of claim 25, wherein the primary stabilizer is used in an amount of about 0.05-0.3 parts per 100 parts of PVC.

34. The additive system as claimed in claim 25, characterized in that the auxiliary stabilizer is used in an amount of about 10-20 parts per 100 parts of PVC.

35. The additive system of claim 25, wherein the secondary stabilizer is used in an amount of about 40-80 parts per 100 parts of PVC.

36. A medical product characterized in that it is made from a polyvinyl chloride composition having an additive system substantially comprising:

About 9.1% by weight of a secondary stabilizer selected from the group consisting of epoxy compounds having less than about 5.2 oxirane groups per molecule.

About 0.015% by weight of external lubricant.

37. The medical product as claimed in claim 36, characterized in that it is produced by extrusion of a polyvinyl chloride composition with an additive system.

38. The medical product as claimed in claim 36, characterized in that it is produced by injection molding a polyvinyl chloride composition with an additive system.

39. The medical product according to claim 36, characterized in that the product is used to contain aqueous solutions, biological fluids and cell tissues.

40. The medical product as claimed in claim 36, characterized in that the product is a tube.

41. The additive system as claimed in claim 1, characterized in that the extractability of the polyvinyl chloride composition measured at 220 nm according to the JPXII method is lower than or equal to 0.08 a.u.

42. The medical product of claim 36, wherein the co-stabilizer has about 2.50 ethylene oxide per molecule.